The invention relates to tissue sampling devices and, in particular, to a biopsy needle for extraction of tissue samples from the human body without surgery.
The present invention finds particular utility with regard to biopsy devices for removing tissue samples from the human body; however, the invention has much broader applications and may be used for selective extraction of tissue samples from other living matter, such as animals, and for postmortem use with regard thereto.
Biopsy instruments in many forms are well known for extracting discrete tissue samples from a human body for microscopic or growth examination of the tissue for diagnostic purposes. Generally, such biopsy instruments take two forms. In one form, the instrument includes a cylindrical cannula having a circumferentially sharpened distal end defining an axial opening substantially coextensive with the interior passage of the cannula. The cannula is inserted into the tissue where the sample is desired and a vacuum is applied to the cannula passage. While maintaining the vacuum, the cannula is withdrawn thereby extracting the tissue which has entered at the distal end of the passage. This is commonly known as end cutting biopsy sampling. In another form, the cannula is provided with a closed or open pointed end and an opening along the side thereof distant from the end. The cannula is inserted into the region where the sample is desired and by means of applied vacuum or inherent tissue pressure, the tissue specimen is drawn through the side opening into the cannula passage. By means of interior or exterior cutting blades, the tissue in the pocket is severed. Alternatively, the edge of the pocket may include a cutting surface such that upon withdrawal of the cannula the captured tissue is severed and retained in the passage. This is commonly known as side cutting biopsy sampling.
Still other samplers employ pivoting cutting legs which surround the tissue sample and are forced together by the sliding action of an exterior sheath to sever and recover the tissue sample. All of these forms require distinctly separate sampling techniques which are provided by a readily available, but mutually exclusive, single function instrument.
Side cutting biopsy sampling, in particular, can present certain hazards. With the closed end needles, because the side pocket is spaced from the distal end, the point of the cannula projects beyond the site where the sample is to be taken. If, in the desired sampling position, the sharpened end projects beyond the tissue site, a blood vessel surrounding the site may be pierced. Because the blood vessel is isolated from the sampling pocket, no blood flows into the pocket and out the open end of the cannula. Moreover, upon withdrawal, there is no visible indication of internal bleeding and accordingly no remedial action undertaken. With the open ended needle, two types of problems are possible because the gap is remote from the tip. If the tip penetrates a vessel there may not be a blood vessel at the gap and the procedure might be stopped incorrectly. In a contrary fashion no blood vessel may be at the end so no blood returns but a blood vessel may be at the gap so that when a sample is taken injury to the blood vessel may occur. Recently developed percutaneous procedures permit visual radiological observation of the instruments inside the body. Biopsy sampling in particular lends itself to such monitoring. However, because of the distance between the tip and the pocket, it may not be possible to accurately locate the pocket at the desired sampling site without incurring the risk that the gap or distal end may penetrate surrounding blood vessels, which are frequently not visible on the radiological monitors. Further, problems are encountered in retrieving only lesion tissue without also severing normal tissue. Because it is not possible to radiologically monitor the position of the pocket, it is possible to align outside the area of tissue and thereby sever and retrieve normal tissue as well. This complicates and may invalidate the resulting diagnosis. Further, the characteristics of lesion tissue vary and may be determinable only during the biopsy procedure. While some tissue is resilient, other tissue may be hard and resistant to penetration. When unexpectedly encountered, the initial instrument may not be suitable for the biopsy and a substitute, specially adapted instrument must be used.
The present invention overcomes the aforementioned deficiencies of the prior art by providing a biopsy needle which readily penetrates and severs tissues of varying texture characteristics and which can be used to provide both end cutting and side cutting biopsy sampling as required and under conditions which permit the area of the cutting action to be accurately radiologically monitored with reference to the instrument position.
More particularly, cannulas according to the present invention are provided with axially and circumferentially open distal ends. The distal end is defined by a beveled tip, the proximate ends of which are contiguous with circumferentially spaced, longitudinally extending cutting surfaces. The channel wall sections may be ground to provide greater sharpness. These walls are preferably sectioned by grinding of the cannula cylinder to define the tip and the cutting surfaces. The axial length of the tip and the cutting surfaces defines the operative length of the cutting surface. The shape of the walls constitutes a radiological profile which can be accurately visually monitored to determine the position of the channel within the lesion. By selecting a channel length commensurate with a lesion site, it can be readily assured that the cutting action of the cannula will take place entirely within the confines of the lesion tissue without concurrent cutting of the normal tissue therearound. In a single cannula embodiment, a stylet is concentrically located in the passage of the cannula and the combination inserted to the edge of the lesion tissue. The stylet is then withdrawn and the cannula axially inserted into the lesion to the desired depth with the beveled tip axially severing the tissue therealong. Thereafter, the cannula is rotated about its axis and the leading or distal cutting edge and the tip are effective to circumferentially sever the circumscribed tissue. After severing, a vacuum is applied to the proximal end of the cannula and the severed tissue is drawn into the needle and thus retained therein during withdrawal of the instrument. Should a blood vessel be nonetheless inadvertently punctured during use of the needle, blood will flow into the passageway and/or out the proximal end of the cannula. This provides a visual warning to the surgeon such that prompt corrective procedures may be undertaken. The cutting action described above provides for the side cutting mode of operation.
The biopsy needle may also employ two concentric cannulas each having a common distal channel profile. The dual cannula device may employed for both side cutting sampling or end cutting sampling. To provide for side cutting, the cannulas are inserted to the lesion site. Thereafter, the cannulas are relatively rotated and the tissue is circumferentially severed by the cutting action between the passing leading edges of the cannulas. Alternatively, the cannulas may be aligned in opposed relationship with the distal walls forming a continuous outer surface and the distal tips providing for axial cutting action during insertion. Upon application of a vacuum, the severed lesion tissue will be drawn into the cannula passage and extracted upon withdrawal of the instrument. Accordingly, a common distal end configuration for the cannulas is provided which enables both sampling techniques to be performed with a single instrument, as elected or required under the biopsy conditions, and in a manner which permits accurate placement and radiological monitoring of the instrument at the biopsy site.
Accordingly, an object of the present invention is the provision of a biopsy needle adapted for both side cutting and end cutting tissue samples.
Another object of the invention is the provision of a biopsy device in which the cutting site can be accurately visually monitored.
A further object of the present invention is the provision of a distal end for a biopsy needle which has an axially and circumferentially open channel defining cutting surfaces effective upon axial or rotational movement of the needle for severing tissue at a biopsy site.
Yet another object of the present invention is the provision of a biopsy needle wherein concentric cannulas can be selectively oriented for both end cutting and side cutting biopsy sampling.
Still another object is the provision of a method for biopsy sampling wherein the size of the lesion tissue to be sampled is radiologically determined, a distal end of a biopsy cannula is provided with a distal cutting channel smaller in size than the lesion, the distal end being inserted into the lesion and the position of the channel radiologically monitored until it is located wholly within the lesion, the cannula thereafter manipulated to sever the adjacent tissue in the lesion, and thereafter applying a vacuum to the cannula during withdrawal to extract the tissue from the lesion site.